The molecular genetic studies of families afflicted with transmissible spongiform encephalopathies (TSEs) is of interest in order to: (1) clarify the distribution of point mutations in the PRNP gene around the world; (2) discover the new mutations associated with the disease; and (3) study association of the mutations with certain disease phenotype. Two new families, one of them of Irish origin, having phenotype of fatal familial insomnia (FFI) were discovered in Australia. One FFI family was found in Ireland. Molecular genetic analysis revealed presence of the pathogenic point mutation D178N on the allele coding for Met at position 129 in these families confirming the diagnosis. One new Creutzfeldt-Jakob disease family carrying the pathogenic mutation at codon 200 Glu to Lys was detected in America. In seven apparently sporadic cases, two point mutations D178N, E299K mutations, 120 bp insertion mutation and three 24 bp deletion mutations were found. This fact points to the importance of evaluation of suspected TSE cases for the presence of PRNP gene mutations. Insertion mutation was detected in a patient from South Africa indicating the wider spread of such mutations.